How to Replace a Dimmer Switch

Turn off power at the breaker, remove the old switch by disconnecting the wires, connect the new dimmer switch wires using wire nuts, and secure it in the wall box.

1. Kill the Power First. Switch off the circuit breaker that controls the light switch. Use a non-contact voltage tester or multimeter to confirm power is off at the switch. Test the voltage tester on a known live circuit first to ensure it's working properly.
2. Extract the Old Switch. Unscrew the switch plate cover and set it aside. Remove the two screws holding the switch to the electrical box. Carefully pull the switch out of the box, leaving the wires attached for now.
3. Document and Disconnect. Take a photo of the wire connections before disconnecting them. Remove the wire nuts or unscrew the terminal screws to disconnect all wires from the old switch. Straighten any bent wire ends with needle-nose pliers.
4. Ready Your New Dimmer. Remove the new dimmer switch from its packaging. Most dimmers come with wire leads instead of screw terminals. Strip about 3/4 inch of insulation from the dimmer's wire leads if not already done.
5. Wire It Up Correctly. Connect the dimmer's black lead to the hot wire (usually black) using a wire nut. Connect the dimmer's red or other colored lead to the load wire (goes to the light fixture). Connect all ground wires together with the dimmer's green ground wire using a wire nut.
6. Seat and Secure. Carefully fold the connected wires into the electrical box. Push the dimmer switch into the box and secure it with the provided screws. Make sure the switch sits flush against the wall.
7. Verify Full Function. Turn the circuit breaker back on. Test the dimmer by turning it on and adjusting the brightness level. If it works properly, attach the new cover plate that came with the dimmer switch.